The present invention relates to the field of electrophotography and particularly to the process step of enhancing the removal of a thin foil, such as a sheet of copy paper, from the surface of a cooperating roll or drum. More specifically, the present invention relates to the xerographic process step of fusing toner to support material by a contact fuser, for example, a hot roll fuser, and to a means of enhancing the removal of the leading edge of a copy sheet as this leading edge emerges from the fusing nip formed by a hot roll and a backup roll.
In the xerographic process a toned visual image is transferred to a copy medium, for example a sheet of copy paper, at a transfer station. The toner is usually a pigmented thermoplastic resin. The individual toner particles are formulated such that they will soften under heat. When soft, they firmly stick to the surface of the copy paper. In order to use the toned copy paper it is necessary to heat the toner to a relatively high temperature, usually in excess of 200.degree. F. One method of so heating the toner is by a contact fuser. One such fuser operates to pass the toned copy sheet through a fusing nip formed by a heated driven fuser roll and a backup roll. This step of contact fusing usually produces a tendency for the toned side of the copy paper to adhere to the surface of the hot roll when contaminants are present on the hot roll. If the sheet of copy paper should adhere to the hot roll, a paper jam or roll-wrap occurs. It is conventional to employ a hot roll having a low energy surface material which enhances release of the copy paper, and in addition, an applicator may be used to apply a release agent to the surface of the hot roll.
The present invention improves the releasing ability of such a hot roll by the use of a tapered guide surface located closely adjacent the hot roll surface a short distance downstream from the fusing nip. The guide surface geometry operates in conjunction with a blowing air jet to create aerodynamic forces which operate to lift the sheet's leading edge from the surface of the hot roll, and to thereafter guide this edge into the nip formed by a drive roll couple located further downstream.
The foregoing and other features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawing.